mirror of
https://github.com/discourse/discourse.git
synced 2024-12-21 02:03:45 +08:00
59 lines
3.1 KiB
JavaScript
59 lines
3.1 KiB
JavaScript
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// Webpack has bugs, using globalThis is the safest
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// https://github.com/embroider-build/embroider/issues/1545
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let { define: __define__, require: __require__ } = globalThis;
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// Traditionally, Ember compiled ES modules into AMD modules, which are then
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// made usable in the browser at runtime via loader.js. In a classic build, all
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// the modules, including any external ember-auto-imported dependencies, are
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// added to the loader.js registry and therefore require()-able at runtime.
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//
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// Overtime, the AMD-ness of the modules, the ability to define arbitrarily
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// named modules and the ability to require any modules and even enumerate the
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// known modules at runtime (require.entries/_eak_seen) became heavily relied
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// upon, which is problematic. For one thing, these features don't align well
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// with ES modules semantics, and it is also impossible to perform tree-shaking
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// as the presence of a particular module could end up being important even if
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// it appears to be unused in the static analysis.
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//
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// For Discourse, the AMD/loader.js mechanism is an important glue. It is what
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// allows Discourse core/admin/wizard/plugins to all be separate .js bundlers
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// and be "glued back together" as full module graph in the browser.
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//
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// For instance, a plugin module can `import Post from "discourse/models/post";
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// because the babel plugin compiled discourse/models/post.js into an AMD
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// module into app.js (`define("discourse/models/post", ...)`), which makes
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// it available in the runtime loader.js registry, and the plugin module itself
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// is also compiled into AMD with a dependency on the core module.
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//
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// This has similar drawbacks as the general problem in the ecosystem, but in
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// addition, it has a particular bad side-effect that any external dependencies
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// (NPM packages) we use in core will automatically become a defacto public API
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// for plugins to use as well, making it difficult for core to upgrade/remove
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// dependencies (and thus so as introducing them in the first place).
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//
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// Ember is aggressively moving away from AMD modules and there are active RFCs
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// to explore the path to deprecating AMD/loader.js. While it would still be
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// fine (in the medium term at least) for us to use AMD/loader.js as an interop
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// mechanism between our bundles, we will have to be more conscious about what
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// to make available to plugins via this mechanism.
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//
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// In the meantime Embroider no longer automatically add AMD shims for external
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// dependencies. In order to preserve compatibility for plugins, this utility
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// allows us to manually force a particular module to be included in loader.js
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// and available to plugins. Overtime we should review this list and start
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// deprecating any accidental leakages.
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//
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// The general way to use it is:
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//
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// import { importSync } from "@embroider/macros";
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//
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// loaderShim("some-npm-pkg", () => importSync("some-npm-pkg"));
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//
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// Note that `importSync` is a macro which must be passed a string
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// literal, therefore cannot be abstracted away.
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export default function loaderShim(pkg, callback) {
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if (!__require__.has(pkg)) {
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__define__(pkg, callback);
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}
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}
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